Fuels for combustion



Patented Apr. 3, 1945 FUELS non COMBUSTION,

Pharis Miller, Elizabeth, and Gould 11. Cloud,

Linden, N. J assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application August 9, 1941,

Serial No. 406,164

4 Claims.

This invention relates, in general, to improvement of hydrocarbon fuelsfor efllcient combustion in combustion engines.

This application is a continuation-in-part of I our application SerialNo. 232,799, which was filed on October 1, 1938, now Patent No.2,268,383, dated December 30, 1941. This earlier application relates toimprovements in ignition qualities of fuels for high speedcompression-ignitionengines by additions of sulfur entirely in freeform, or partly in the free form and partly combined.

The present application is concernedmore specifically with the use ofsulfur combined with amino groups as in hexasulfamide to improveignition qualities of the compression-ignition engine fuels.

Combustion engines, more particularly, high speed compression-ignitionengines, are generally referred to by the name of their prototype, theDiesel engine. 'Hydrocarbon fuels which have been found most suitablefor these engines are crude oil distillates which are highly paraflinic,but these fuels are limited in supply and relatively expensive. i

In consideration of increasing power and fuel economy with eliminationof vibration harmful to the mechanism. in the operation ofcompresconsisting of normal cetane and the aromatic compoundalpha-methyl naphthalene 'is shortened very nearly in proportion to theincrease in percentage of cetane by volume, the ignition quality of afuel can be measured in terms of the cetane content of such a blend.Accordingly,

when the improvement in a fuel by a small ,amount of addition agentcorresponds to an improvement by an increased about 5% or more of cetaneby volume in a blend withalpha-methyl naphthalene, such an additionagent is considered to have commercially significant effectiveness,provided the addition agent used is not very costly in comparison withthe value of the fuel.

Attempts have been made to find substances effective for improvingignition qualities of Diesel fuels, but various substances determined tobe efiective for this purpose are not altogether satisfactory from allpoints of view for commercial use. For example, a number of theeffective promoters, such as alkyl nitrates, are rather ex-' pensive atpresent, some are too unstable, some are excessively corrosive, and someare not readsion-ignition engines, principally whenthe hy-s 1 drocarbonfuel contains insufficient amounts of hydrocarbon compounds recognizedas serving these ends by virtue of their suitable ignition qualities,the addition of various chemical substances to the fuels hasbeenproposed.

Hydrocarbon compolmdscharacterized'by aromatic, other cyclic, and highlyunsaturated hydrocerbons have poor ignition qualities as Diesel enginefuel ingredients, following from the fact that hydrocarbon fuelscontaining a. large proportion of these compounds fail to undergo promptand smooth combustion in representative types of engines in whichunsuitablecombustion is manifested by'e'ngine vibrations and annoyingsounds;

A poor ignition quality in a compression-ignition engine fuel isexhibited by an excessive ignition lag, in other words, an excessivedelay between the beginning of fuel injection into the combustionchamber of the engine and the point at which ignition of the fuel setsin. In contrast, the normal hydrocarbon cetane, which serves as astandard of high ignition quality in Diesel fuel rating byrecommendation of the S. A. E. Volunteer Group for Compression-IgnitionFuel Research, has a desirable minimum is- SGNH2 or SlsNsH:

.1 being undetermined specifically, but being usually of the order of 5or more; and in this composition produces almost the same cetane numberincrease as does free sulfur when added to a Diesel fuel, while having amuch lower copper strip corrosion action and higher solubility. Toobtain a combination of sulfur with the amino group, ammonia may bereacted with a sulfur chloride or sulfur may be reacted with emmania. Aconvenient method used to prepare hexasulfamide in good yields B one inwhich ammania is passed through a solution of sulfur monochloride inchloroform, the reaction mixture being cooled by heat exchange with afreezing mixture in the early part of the reaction to prevent violentreaction, and after darkening of nition lag. Since the ignition leg .ofa blend colon ev m a nincreaseintemperature. The admission of ammoniawas continued until the reaction mixture color became salmon red. Fromthe resulting reaction products, ammonium chloride was filtered ofi.Alternatively, the ammonium chloride may be removed by extraction withwater. Other low boiling alkyl halide diluents, such as ethylenedichloride; may

be used in place of chloroform. ,With increase of cluding free sulfur,may be added together to theoil. Hexasulfamide crystals may bevrecovered gravities, and highheat values, such oils being procured fromnaphthene base, asphalt base, or mixed base stocks. Heavier and lowergrades of petroleum oil, such as residual oils, are even made moresuitable for slow speed engines.

The burning qualities of fractions from paraffin crudes or hydrogenatedoils are also enhanced by the novel addition agent of this invention.

Small quantities of these novel addition agents may be used for adaptingvarious mixtures of hydrocarbons for use as Diesel fuels, includingrecycle stocks from cracking operations, nonparaflinic extracts, oilsfrom destructive distillations of pyro-bituminous and asphalticmaterials, and mixtures of these with one another or with crudepetroleum fractions. With improvefrom the chloroform solution in whichit is.pre-.

pared by fractional crystallization due to the relatively greatersolubility of the hexasulfamide in organic solvents. solution is firstevaporated down to about a fourth of its original volume, then, uponaddition of 95% ethyl alcohl, in excess, a by-product comprisingsomefree sulfur comes out of solution. After filtering .off the by-productprecipitate, reconcentrating the filtrate, and diluting the concentratewith benzene, hexasulfamide is crystallized out from the benzene byaddition of aqueous alcohol. Purified hexasulfamide, obtained byrecrystallization, is insoluble in and stable towards water, odorless,non-explosive, and stable to air. Cetane number tests on a Diesel oilcomposed of a Colombian gas oil and containing only 1.5% of the animatedsulfur show that this addition agent gives the fuel a cetanenumberincrease of +10 or +11. v

Owing to its good'stability to air and moisture, and to the ease withwhich it is dissolved in a hydrocarbon fuel, hexasulfamide is a verysuitable agent for addition to a fuel on its passage to the engine fromthe engine supply tank.

The proportion of hexasulfamide to be added to a hydrocarbon fuel foreffecting improvement in ignition. ranges from a fraction of I% to itslimit of solubility in the fuel, and, as needed. Preferably it is usedin concentrations from about 0.1% to 5% by weight, although when it isused with a more potent agent, such as free sulfur, it need not be usedin as large amounts to obtain a certain cetane number increase.

A gas oil boiling from about 400 F. to 700 F. or 750 F., or, in general,having a suitable boiling For example, the chloroform range andviscosity for use as a fuel in Diesel type engines, may be used as thehydrocarbon fuel.

Under some circumstances, a more narrowly cut fraction, such as onedistilling from 400 to 600 F. or from 500 to 700 F. may be used.Ordinarily, the hydrocarbon fuel may be said to have a boiling rangeabove that of gasoline.

This invention makes commercially feasible the preparation of Dieselfuels giving satisfactory engine performance from crude oils, gas oils,and residual fuels having low pour points. low A. P. I.

ment in the ignition qualities of the hydrocarbon fuels mentioned byaddition of inexpensive agents herein disclosed better performance of 2.Diesel engine operating on the improved fuel is obtained-in the way ofeasier starting, smoother idling, silent running, and absence of shockloading.

It is not intended that this invention be limited to the specificexamples which are given merely for the sake of illustration, but it isdesired to claim all the novelty inherent in this invention in theappended claims as broadly as the prior art permits.

Other agents for enhancing various other qualities without detractingsubstantially from the the Diesel type which comprises a hydrocarbonDiesel fuel and a sulfur-containing ignition promoter consistingessentially of hexasulfamide containing no free sulfur in an amountsufficient to improve the ignition quality of the fuel.

2. A Diesel fuel comprising a hydrocarbon Diesel fuel containing about0.1% to about 5% by weight of hexasulfamide containing no free sulfur.

3. A method of accelerating ignition of a Diesel fuel which comprisesadding to the fuel prior to its ignition a small amount of asulfurcontaining ignition promoter consisting essentially ofhexasulfamide containing no free sulfur sufficient to substantiallyincrease the cetane number value of the fuel.

4. A Diesel fuel comprising a major proportion- PHARIS MILLER. GOULD H.CLOUD.

